Compression question

[Soldier Mo]

So, I put a WAI on my GA about two months back and have been waiting for the parts to come in for my exhaust before I convert it to a CAI. In the time I have had to think between projects, how much would it take to change the compression ratio on a 3100? I know these engines can take an alright amount of boost safely, but raising the compression ratio increases power as well, right? What kind of gains do you think are possible?

[Matt95GT]

Cost = price of new custom pistons + install
Higher compression will yield more power. If you plan on running boost, you do not want to raise the compression, usually it is desirable to lower it instead to handle more boost safely.

[Soldier Mo]

What kind of NA results are possible with a higher compression ratio, then? I figure since I am running the 3100 and I would have to get just about everything custom made/fitted for it anyway (SC or Turbo) it might be cheaper and safer to just raise the compression ratio. Thoughts?

[Dave C]

... if the heads can handle it. you may also have to use higher octane fuel. sorry, not familiar enough with the benefits to give you any meaningful information on increased performance.

[Blackhawk]

Couldn't milling the heads and intake down a bit raise the ratio slightly?

[SappySE107]

3.1 camaro pistons drop right in. I don't know the exact compression, but its substantial (11.5-12:1 I believe) We have ran 12.4 on pump gas, 11.5:1 on regular (with headers) and on midgrade (3400, no headers). Its not cheap and you should consider a larger cam to go with the increased compression. Port work would go a LONG way on a high compression motor, and tuning is going to be very important.

Milling the head is worth a little but nothing to spend the time and money on. If they have to come off anyway, then sure but to do it for that is not cost effective.

[Soldier Mo]

3.1 camaro pistons drop right in. I don't know the exact compression, but its substantial (11.5-12:1 I believe) We have ran 12.4 on pump gas, 11.5:1 on regular (with headers) and on midgrade (3400, no headers). Its not cheap and you should consider a larger cam to go with the increased compression. Port work would go a LONG way on a high compression motor, and tuning is going to be very important.

Milling the head is worth a little but nothing to spend the time and money on. If they have to come off anyway, then sure but to do it for that is not cost effective.

Did you get any dyno results?

[SappySE107]

hmm, well I know the stock 3400 heads and lower, ported 3500 upper, 70mm TB, pretty good sized cam (.539" lift 230s duration at .050") and 3.4 camaro pistons made 176 whp using the OBD1 computer (this was a swap into 93 grand prix (or similar year). I don't know what the 3100 made, or if it was ever dynoed. I don't think it was.

It was still making power at 6800 rpm.